Invalidity dossier
US 5890791
Light control sheet, surface light source unit and liquid crystal display device
Current assignee: Konica Minolta Inc
Added 9/23/2026, 9:16:58 PM
Active provider: DeepSeek · deepseek-flash
Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,890,791 A
Title: "Light control sheet, surface light source unit and liquid crystal display device"
Assignee/Applicant: Konica Minolta Inc. (listed as current assignee); originally assigned to KONICA CORPORATION via assignment from inventor Shinichiro Saito.
Inventor: Shinichiro Saito
Key dates:
- Priority date: 1995-10-13
- Filing date: 1996-10-09 (application US08/731,021)
- Publication/grant date: 1999-04-06
- Status: Expired – Lifetime (anticipated expiration 2016-10-09)
Purpose: The invention addresses problems in conventional light control sheets used in liquid crystal displays. In the prior arrangement, each prism had symmetric boundary surfaces forming an equilateral triangle; light entering such a sheet behaved as if passing through a slanted transparent plate, so only the angle of emergence changed while the light distribution shape itself could not be controlled — meaning neither maximum luminance, half-value degree, nor side lobe light could be adjusted. The stated objects are (1) to provide a light control sheet, surface light source unit, and liquid crystal display device capable of controlling maximum luminance, half-value degree, and side lobe light, and (2) to provide a light control sheet free from luminance unevenness.
Plain-language scope: The disclosed light control sheet has prisms on at least one side, with generatrices parallel to one another, so light entering through the prism side exits the other side. Each prism, viewed parallel to the generatrices, has two boundary surfaces meeting at a vertex that are asymmetric about a line through the vertex perpendicular to the sheet surface, and at least one boundary surface is nonplanar (e.g., a curved convex or concave surface). The claimed concepts extend to surface light source units and liquid crystal display devices incorporating the sheet, and cover various combinations where one or both boundary surfaces are planar or curved.
Source: https://patents.google.com/patent/US5890791/en
What the excerpt does not establish: It does not provide the full claim text, complete specification, drawings, prosecution history, or any legal conclusions about validity, enforceability, or infringement. All cited material is limited to the supplied excerpt.
Generated 10/1/2026, 9:34:26 PM
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Litigation summary
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Proceedings on file (0)
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PTAB challenges
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Assignment history
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Prior art
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Obviousness
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Extensions
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Derivative works
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